The field of integrated circuit packaging is one of the most evolutionary fields connected to semiconductor manufacturing. As demand for devices that are smaller and more powerful continues to increase, pressures are put on manufacturers to develop better and more efficient ways to assemble and package IC products. One of the more recently developed methods for assembling and packaging IC products is known as Ball-Grid-array (BGA) technology. Motorola.TM. inc. is one of the more noted pioneers of BGA technology. Currently there are many companies that license BGA technology developed by Motorola.TM..
BGA technology, which uses solder balls instead of interconnect leads, offers several advantages over more mainstream technologies such as Fine-Pitch-Technology (FTP), and Pin-Grid-Array (PGA). One obvious advantage is that there are no leads that can be damaged during handling. Another advantage is that the solder balls are self-centering on die pads. Still other advantages include smaller size, better thermal and electrical performances, better package yields, and so on.
In typical BGA assembly, an array of metallic die pads provided in a substrate or wafer is fluxed during a fluxing operation in preparation for insertion of individual solder balls one per pad. After the solder balls are placed into the array of pads, a next operation involving a heat process causes the solder balls to be soldered to the individual pads performing the connecting mechanisms for surface mounting.
The above-described fluxing operation conventionally involves the use of a plate having a specific array of openings placed therein for the purpose of retaining an identical array of same-length pins, which are mounted into the openings. The resulting fixture is then placed into a source of flux material and touched to the die-pad array thus transferring flux material to each individual die pad simultaneously. Generally speaking, the arrangement of openings and mounted pins specific to a flux fixture is identical to a specific arrangement of die pads on a given substrate.
Problems can accrue with respect to the method described above, specifically regarding the physical aspects of and vulnerability of the fluxing fixture itself. For example, it is a difficult process to ensure that all pins specific to a fixture are mounted such that they are protruding at a same length. If some pins are shorter than others in a complete fixture, then the associated die pads on a given substrate will not receive the proper amount of fluxing. In addition to length variances, perpendicularity variances with regard to individual pins and their positions of mounting within the provided openings of the flux plate cause the pin surfaces of the non-perpendicular pins to form a non-coplanar relationship with their associated die pads. This results in improper delivery of the flux material to the die pads. It is further noted that prior-art pins and openings are restricted by practicality to being round, which is another disadvantage in flux application.
What is clearly needed is a fluxing fixture that is formed of one-piece such that all of the pins are physically identical to each in cross-section and length and retain identical positions with respect to the surface of the fixture. A fixture such as this would streamline the fluxing operation in BGA assembly by providing a physically consistent interface between the surfaces of each pin and their associated die pads when transferring flux material.